Ejection of rocky and icy material from binary star systems: implications for the origin and composition of 1I/‘Oumuamua

Abstract

In single star systems like our own Solar system, comets dominate the mass budget of bodies that are ejected into interstellar space, since they form further away and are less tightly bound. However 1I/'Oumuamua, the first interstellar object detected, appears asteroidal in its spectra and in its lack of detectable activity. We argue that the galactic budget of interstellar objects like 1I/'Oumuamua should be dominated by planetesimal material ejected during planet formation in circumbinary systems, rather than in single star systems or widely separated binaries. We further show that in circumbinary systems, rocky bodies should be ejected in comparable numbers to icy ones. This suggests that a substantial fraction of additional interstellar objects discovered in the future should display an active coma. We find that the rocky population, of which 1I/'Oumuamua seems to be a member, should be predominantly sourced from A-type and late B-star binaries.

1I/‘Oumuamua as a Tidal Disruption Fragment from a Binary Star System

“…Jackson et al (2017) state that their simulations did not find any cases where a planet would be tidally disrupted by a close stellar passage before being ejected, indicating that such disruptions are very rare. In this section I will address the claims of Jackson et al (2017) with the help of a simple numerical simulation. Figure 1 shows a numerical simulation of a binary system, with a planet initially orbiting the more massive component.…”

“…After the original version of this paper was submitted (and a preprint made public), Jackson et al (2017) have published numerical simulations of planetesimal scattering in binary systems. Jackson et al (2017) state that their simulations did not find any cases where a planet would be tidally disrupted by a close stellar passage before being ejected, indicating that such disruptions are very rare.…”

“…1 was literally the first simulation I attempted of an instability with a planet starting on a S-type orbit (orbiting one of the stars; nomenclature from Holman & Wiegert 1999). Jackson et al (2017) in contrast integrated only P-type orbits, where their particles initially orbited both stars. I also did a quick test of planets initially on P-type orbits, and obtained results consistent with those of Jackson et al (2017), as the planet never comes very close to either of the stars before being ejected.…”

“…Jackson et al (2017) in contrast integrated only P-type orbits, where their particles initially orbited both stars. I also did a quick test of planets initially on P-type orbits, and obtained results consistent with those of Jackson et al (2017), as the planet never comes very close to either of the stars before being ejected. Therefore, results of Jackson et al (2017) show that tidal disruption is unlikely only for initially P-type planetary orbits, but have no relevance for S-type orbits, which appear to hold much more potential for tidal disruption.…”

Collisional elongation: Possible origin of extremely elongated shape of 1I/‘Oumuamua

“…It is recognized to be an interstellar object because of its high orbital eccentricity e ≈ 1.2. A considerable fraction of planetesimals are ejected from planetary systems during the planet formation stage (Fernandez 1978;Bottke et al 2005;Raymond et al 2018;Jackson et al 2018); thus it is no wonder that interstellar objects exist. Moreover, the velocity at infinity v ∞ ≈ 26 km/s of 1I/'Oumuamua is close to relative velocities of stars in the solar neighborhood.…”